1. Field of the Invention
The present invention relates to a semiconductor device and its manufacture method, and more particularly to a semiconductor device having photoelectric conversion elements and its manufacture method.
2. Related Background Art
A conventional image pickup module has a semiconductor chip with light reception elements and a substrate having lenses for converging light on the light reception elements. The semiconductor chip and substrate are mounted on both sides of a spacer to be spaced apart by some distance. Light can be converged on a light reception plane of each light reception element so that a real image can be formed.
FIGS. 18A, 18B and 18C are broken perspective views illustrating a conventional image pickup module manufacture method. FIG. 18A shows a substrate 917 having lenses for converging light on a light reception element, FIG. 18B shows a spacer 901, and FIG. 18C shows a semiconductor chip 503 having light reception elements 100. According to a conventional image pickup module manufacture method, the substrate 917 and semiconductor chip 503 are bonded on both sides of the spacer 901 to form an image pickup module. If each of a plurality of image pickup modules is manufactured by this method, a number of manufacture processes are required including an alignment process for the semiconductor chip 503 and substrate 917.
FIGS. 19A, 19B and 19C are schematic cross sectional views illustrating another conventional image pickup module manufacture method.
FIG. 19A is a schematic cross sectional view of a semiconductor wafer 910 formed with a plurality of semiconductor chips, the wafer having some warp caused by a passivation film or the like formed by a semiconductor device manufacture process. This warp has a height difference of, for example, about 0.2 mm between the highest and lowest positions in the case of an 8-inch wafer. A wafer with a warp has a roll shape, a saddle shape, a bowl shape or the like.
As shown in FIG. 19B, the warp of the semiconductor wafer 910 is removed by sucking the bottom surface of the wafer 910 by using a jig 950.
Next, as shown in FIG. 19C, the semiconductor wafer 910 and a substrate 917 are bonded together via a spacer 901.
Thereafter, suction of the semiconductor wafer 910 is released to dismount the semiconductor wafer 910 and lens substrate 917 from the jig 950. This assembly of the semiconductor wafer and lens substrate is cut along each semiconductor chip and lens to form an image pickup module. A method of bonding together the semiconductor wafer 910 with semiconductor chips and the substrate 917 by a single alignment process is suitable for the manufacture of a plurality of image pickup modules.
(First Technical Issue)
After the semiconductor wafer 910 is bonded via the spacer 901 to the lens substrate 917 having a plurality of lenses for diverging light on light reception elements, each image pickup module is formed by dicing the substrate along each scribe line between semiconductor chips. During dicing, a force is applied to the substrate 917 from a dicing blade. This force may change the surface shape of a lens and hence a reflectivity thereof, degrading a focussing performance.
It is therefore an object of the invention to efficiently manufacture a semiconductor device such as an image pickup module without changing the surface shape of a lens during dicing.
(Second Technical Issue)
With the manufacture method illustrated in FIGS. 19A to 19C, after suction of the semiconductor wafer 910 is released, the semiconductor wafer 910 tends to recover the original warp state. If the lens substrate 917 is bonded to the semiconductor wafer 910 with a warp on the convex surface side, the semiconductor wafer 910 and lens substrate 917 are likely to be peeled off in the peripheral area of the semiconductor wafer 910.
Conversely, if the lens substrate 917 is bonded to the semiconductor wafer 910 with a warp on the concave surface side, the semiconductor wafer 910 and lens substrate 917 are likely to be peeled off in the central area of the semiconductor wafer 910.
If the semiconductor wafer 910 and lens substrate 917 are peeled off at the worst, or if an adhesive layer between the semiconductor wafer 910 and lens substrate 917 is elongated, the distance between the semiconductor wafer 910 and lens substrate 917 changes so that light cannot be converged correctly on the light reception element, disabling desired image pickup in some cases.
It is therefore another object of the invention to manufacture a semiconductor device such as an image pickup module capable of realizing reliable image pickup by considering a warp of a semiconductor substrate such as the semiconductor wafer 910.
According to one aspect of the invention, there is provided a semiconductor device formed by cutting a first substrate and a second substrate bonded together by a spacer, wherein: the spacer is disposed at an end of the first substrate after cutting; the second substrate is a semiconductor wafer formed with a light reception element or elements; and the first substrate has an optical element or an optical element set for converging light on the light reception element or elements.
According to another aspect of the present invention, there is provided a semiconductor device manufacture method comprising: a step of bonding a first substrate and a second substrate by using a spacer; and a step of cutting the first and second substrates, wherein the step of cutting the first substrate cuts the first substrate at a position where the spacer is disposed under the first substrate.
According to still another aspect of the present invention, there is provided a semiconductor device manufacture method comprising: a step of holding the semiconductor substrate on a base under a condition that the warp is removed; a step of bonding an opposing substrate to the semiconductor substrates with a size adjusted according to the warp of the semiconductor substrate; and then a step of cutting the opposing substrate.